Wells has led studies to investigate the relation between use of WDGS in feed and the incidence and persistence of Escherichia coli O157:H7 in cattle manure and on the animals' hides.

Cattle are a natural reservoir for the microbe. It is apparently harmless to them, but can cause illness in humans. E. coli in manure can newly infect or reinfect animals in pastures and feedlots; if E. coli ends up on the animals' hides, it could subsequently contaminate meat and equipment at the packinghouse.

In early experiments with 608 steers, Wells and his colleagues at Clay Center showed that the incidence and prevalence of E. coli O157:H7 in manure, and the incidence on hides, was significantly higher for cattle whose corn-based feed included 40 percent WDGS than those whose feed did not include WDGS.